Magazine

Guess What's the New Buzz in Hearing Aids

April 29, 2001

The Ormia Ochracea fly is a supercritter when it comes to hearing. Most flies have no sense of hearing at all, but this one can home in on the sound of a chirping cricket to within two degrees--a feat unmatched even by humans. Now that knowledge is being studied for use in a new generation of supersensitive hearing aids.

Humans locate the sources of sounds by using "phase cues"--sensing, for example, that the source is on the right because the sound reaches the right ear first. Ormia does the same thing. And it's a remarkable feat, considering that the distance between its ears is only half a millimeter. At that scale, say scientists at the University of Toronto and Cornell University, the phase difference between the two ears would normally be considered too small to provide clues on direction.

Not anymore. In a report in the Apr. 5 issue of Nature, the scientists describe the Ormia's amazing ability and its high-tech implications. Placing flies on a treadmill made from a Ping-Pong ball, they played cricket recordings from various directions, and followed the flies' movements with a computer. To the surprise of the researchers, the flies closely tracked the sound, automatically changing direction to match the chirping source.

According to Andrew C. Mason, the University of Toronto researcher who led the study, the Ormia's ears function precisely the way an ideal hearing aid should, gauging the phase shift between the ears, and using the molecular equivalent of a directional mike to filter out background noise.

The team now aims to develop a prototype hearing aid that imitates the fly's ears. They plan to build the world's smallest directional mike--roughly one-third the size of today's tiniest devices--and fit it into an in-the-ear hearing aid. The device could be on the market in less than five years. Research over the last couple of decades has shown that vegetable oil, with very minor modifications, can serve as diesel fuel in cars, lubricating oil in engines, and even heating oil for homes. Both corn and soybean oil produce fewer fumes than petroleum-based fuels and are more environmentally friendly to extract. One problem: At current prices, vegetable oils are two to three times more expensive than petroleum. A discovery by Iowa State University scientists could change all that, however, allowing biologists to engineer plants that produce far more oil than today's crops.

Corn and soybeans, like most plants, naturally generate oil as they grow. To force plants to pump out more oil per bushel of seed, scientists need to know which genes control the process. By consecutively knocking out each candidate gene and then measuring the effect on oil production, the Iowa team was able to identify a key player, which codes for a specific cellular enzyme called pyruvate dehydrogenase. Their results are summarized in a recent issue of Plant Physiology.

The scientists next hope to engineer a corn strain that produces higher levels of pyruvate dehydrogenase, and as a result, more oil. "Down the line is creating an energy source we control," says David J. Oliver, botany professor and one of the study's authors. "We can always grow our own corn, even if we cannot pump our own oil." The clamshell containers that hold burgers and other fast-food sandwiches continue to evolve. First came foamed-plastic containers that were puffed up using chlorofluorocarbon gas. Decidedly un-green. Cardboard versions have also made an appearance, but they are expensive to produce and don't keep food warm for long. Now, scientists at the U.S. Agriculture Dept. are designing biodegradable clamshells made from wheat. Fiber from the stalk provides insulation, and starch from the kernel holds the composite together.

Manufacturers already produce environmentally friendly clamshells from potato starch. But USDA researchers claim there aren't enough spuds in North America to satisfy the fast-food industry's demand. Wheat-based containers could fill the bill since the U.S. cranks out more than 30 million tons of wheat each year, much of which is either burned or plowed under. -- Hepatitis C is notoriously easy to catch. The virus, which leads to chronic liver disease, may be transmitted sexually or passed on by shared razors, needles, and even toothbrushes. Now, doctors suspect another common route: getting a tattoo. Researchers at the University of Texas Southwestern Medical Center at Dallas found that people with tattoos were nine times more likely to be infected with hepatitis C than people without tattoos. Of the 626 patients studied, few of those who had tattoos and hep C were likely candidates for other modes of transmission--leading scientists to pinpoint infected needles as the cause of the illness.

-- A tropical grass called miscanthus, similar in appearance to bamboo, may soon be lending its strength to biodegradeable plastics used in car parts, says University of Warwick materials professor Nick J. Tucker. The hardy grass, which requires little maintenance, can grow up to nine feet tall in temperate climates. Best of all, when it is time to put a car out to pasture, parts made from this grass could be composted. There is just one hurdle, Tucker says: Designing biodegradable parts that are safe and can absorb significant impact. The researchers also hope to put the grass in board products, paper pulp, compressed fuel briquettes, garden candles, and even soaps.